1. Field of the Invention
This invention relates to insulation techniques and more specifically to methods and apparatus for high reflectivity thermal insulation in exhaust ducts, and the like.
2. Description of the Prior Art
Stacks, flues, chimneys, and the like are common industrial and domestic devices. Because these duct structures frequently are used to promote gas to flow from a furnace or oven to the atmosphere for safe dispersal, it often has been necessary to insulate these ducts thermally in order to protect lives and property from fire or heat damage. Masses of fibrous material, or "lagging", that has a low thermal conductivity, usually is placed over the ducting. These materials reduce the surface temperature of the duct structure to some relatively safe level.
Although these materials provide generally effective thermal protection, they are, nevertheless, subject to a number of disadvantages. This fibrous lagging, for example, deteriorates with the passage of time and with exposure to high temperatures and thermal cycling. Naturally, this deterioration must be arrested through relatively frequent patching and painting. There also is a certain amount of dust and debris that is associated with fibrous thermal insulation. This particulate matter, moreover, can present very serious sanitary problems and health hazards, if the insulation is used in a bakery or other type of food processing plant, because the fines can be incorporated in the foodstuffs.
Installing these fibre-insulated stacks also requires the services of at least two classes of costly skilled labor-tinsmiths for assembling the duct and "insulators" for installing the lagging.
Clearly, there is a need for insulated ducting that is clean, simple to install, and suitable for long years of essentially maintenance-free operation.